1. Field of the Invention
The present invention relates to a light emitting unit, a manufacturing method thereof and a touch panel having the same. In particular, the present invention relates to a light emitting unit having an asymmetric light pattern.
2. Description of Related Art
Depending on the design of the electronic product, the electronic product is controlled by the input devices such as a key, a keypad, a tracking ball, or a touch panel screen. Recently, the touch panel screen has been widely used in electronic applications. The touch panel screen includes a touch panel which has a transparent panel with a sensitive surface to cover the displaying area of the screen. Users can select the items or move the cursor by using a finger or a touch pen on the touch panel screen so that the electronic device is controlled by the touch signals from the touch panel screen. For example, an IR proximity sensor is widely used in mobile communication devices, such as IR touch panel, for detecting the face of users so as to control the mobile communication device.
The IR touch panel has LEDs and receivers arranged on four sides of the screen. The lights emitted from LEDs construct a net of IR. Thus, when user's finger is blocking one or more of the lights, the position of the finger relative to the screen can be determined. However, the traditional SMD LEDs have symmetric lighting pattern in two directions; therefore, the view angles at X axis and Y axis of the screen are usually equal to each other. The LEDs having symmetric lighting pattern is not suitable for the touch panel, because the touch panel only detects the object in one direction, i.e., the user' finger closes to the screen substantially from the front side (Y axis) of the screen. Thus, the lights project at the right and left sides (X axis) of the screen have no function. Even more, the symmetric lighting pattern at axis and Y axis may induce the signal crosstalk which results in the short detecting distance of the touch screen. User's finger has to close to screen to position his finger if the touch screen has a short detecting distance. In other words, the detecting sensitivity is reduced. Furthermore, the touch screen may be scratched by the user and the lifetime of the screen is reduced.
On the other hand, the light intensity is divided to the X axis and Y axis equally in the traditional LEDs; therefore, the light brightness toward the user's eyes at Y axis of the screen is low. In other words, the lights project toward the user's eyes does not have enough brightness when user watches the screen.